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Genome evolution of endosymbiotic bacteria in blood-sucking insects
ŘÍHOVÁ, Jana
The research on insect-bacteria symbiosis is experiencing a rapid burst leading to the identification of much higher complexity and dynamics of the insect-bacteria associations than ever before envisaged. The generally accepted concept of obligate bacterial symbionts as providers of essential compounds (vitamins, aminoacids) has been further developed into the framework of microbiomes, i.e. communities of microorganisms associated with the host. The majority of the knowledge has been derived from plant sap-feeders, while data on blood-feeding insects remain fragmented and even inconsistent. In this thesis, we employ amplicon, genomic and in-vivo approaches to investigate several symbiotic systems of obligate blood-feeders and address the following questions: What is the diversity of symbiotic bacteria in our studied systems? What are the metabolic capacities of these symbionts? What is the role of symbionts in the biology of their hosts? What are the possible sources of bacteria prone to establish symbiosis with obligate blood-feeders? Where these symbionts reside in the host´s body? What is the coevolutionary pattern of these bacteria with their hosts? As an answer to these questions, I present the results detailed in the course of this thesis, which are preceded by a comprehensive introduction to the studied topics and wraps up with a summary of the main results.
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Population structure of the gray wolf (Canis lupus)
Říhová, Jana ; Hulva, Pavel (advisor) ; Pivnička, Karel (referee)
Gray wolf (Canis lupus), is historicaly the most widespread carnivore with the former range including most of the northern hemisphere. The ambivalent relationship of humans to this predator resulted in extermination of this species in many areas, on the other hand led to the evolution of the dog, unique domesticant with vast phenotypic variation. The effort of conservation biology in last decades resulted in the shift of perception the role of big carnivores in ecosystems, with consequent recolonization of many regions by wolf, including the Czech republic. This changes brings the elevation of interest in this taxon by both experts and laymans. Present review aims to assemble published information regarding distribution, phylogeography, population structure, social and spatial behaviour of the gray wolf. The chapters describing the domestication process of the dog and hybridization with his wild ancestor are included.
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Perception of climate change impacts and adaptive capacity in organic agriculture
Říhová, Jana ; Vačkářová, Davina Elena (advisor) ; Pražan, Jaroslav (referee)
This thesis deals with the perception of climate change issue and adaptive capacity of organic farming systems in the Czech Republic. The aim of this thesis it to investigate organic farmers' attitudes toward climate change and their willingness to adopt adaptation practices. The method used in this thesis is based on questionnaires that were distributed among organic farmers in the period of January-March 2015; 52 questionnaires were subsequently analysed. The results indicate that the majority of organic farmers surveyed believed that the global climate change is occurring, expected negative climate change effects and observed higher frequency of extreme weather events. Most of the respondents also acknowledge the importance of adaptation practices and their own responsibility in adaptation. The statistical analysis revealed that both the belief about climate change and perception of associated threats may serve as predictors of the willingness to implement adaptation measures.
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The impact of dividend policy on firm value
Říhová, Jana ; Dědek, Oldřich (advisor) ; Janda, Karel (referee)
This thesis is focused on the dividend policy in the Czech Republic. We describe the basic about dividends as types of dividends, process of declaration and payments, dividend-paying methods, determinants which can influence the dividends and so on. The main part is devoted to the issue of dividend policy in the Czech Republic and its impact on the firm value. We use the event studies, based on observing the abnormal returns to shareholders around the record date. Then we apply regression of abnormal returns on relevant explanatory variables. And we also make an analysis of some of explanatory variables, as volume and dividend yield. Finally, we also shortly mention the share repurchase, the alternative to the dividend payout.
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Vliv dividendové politiky na hodnotu firmy
Říhová, Jana ; Dědek, Oldřich (advisor) ; Janda, Karel (referee)
This thesis is focused on the dividend policy in the Czech Republic. We describe the basic about dividends as types of dividends, process of declaration and payments, dividend-paying methods, determinants which can influence the dividends and so on. The main part is devoted to the issue of dividend policy in the Czech Republic and its impact on the firm value. We use the event studies, based on observing the abnormal returns to shareholders around the record date. Then we apply regression of abnormal returns on relevant explanatory variables. And we also make an analysis of some of explanatory variables, as volume and dividend yield. Finally, we also shortly mention the share repurchase, the alternative to the dividend payout.
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Legionella Becoming a Mutualist: Adaptive Processes Shaping the Genome of Symbiont in the Louse Polyplax serrata
ŘÍHOVÁ, Jana
Genomic modifications coupled with the first known transition of a Legionella bacterium to symbiosis with insects (louse Polyplax serrata). Apart from characteristics typical for other obligatory symbionts in insect (genome reduction), the main innovation of the genome consists in horizontal acquisition of complete biotin operon. Comparative genomic analysis with free living legionellae and other symbiotic bacteria demonstrates convergent evolution of several phylogenetically unrelated louse symbionts.
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Evoluce genomu bakteriálních symbiontů vši \kur{Polyplax serrata} (Phthiraptera, Anoplura)
ŘÍHOVÁ, Jana
Blood-sucking louse Polyplax serrata harbor two phylogenetically distinct symbiotic bacteria from the orders Legionellales (Gammaproteobacteria) and Neisseriales (Betaproteobacteria). Based on rigorous phylogenetic analyses, the first bacteria was confirmed as member of genus Legionella, and the name Candidatus Legionella polyplacis, sp. n. was proposed. Vertical transgeneration transmission was proved by visualisation of the symbiont in host tissues. Improved genome of latter symbiont is considerably larger and possesses more metabolic functions. In the genome, I found horizontally transferred operon, which encode synthesis of enzymes involved in urea cleavage.
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